RA-13-03728 Enclosure Page 1 of 18

Petition for Exemption from 14 CFR 25. 841(a)(2) and 25.841(a)(3) Amendment 25

- 87 for Uncontained Engine Failure.

Name and Address of the Petitioner

Douglas Lane, Deputy Lead Administrator The Boeing Company PO Box 3707, M/S 03-56 Seattle, Washington, 98124

Section(s) of the Re gulation(s) from whic h Relief is Needed:

25.841(a)(2) and 25.841(a)(3) With Respect to Uncontained Engine Failures.

§ 25.841 (a)(2) The airplane must be designed so th at occupants will not be exposed to a cabin pressure altitude that exceeds th e following after decompression from any failure condition not shown to be extremely improbable: (i) Twenty-five thousand (25,000) feet for more than 2 minutes; or (ii) Forty thousand (40,000) feet for any duration.

(a)(3) Fuselage structure, engine and sy stem failures are to be considered in evaluating the cabin decompression.

Extent of Relief Needed and Reason(s)

Regulation Requires: Relief is Necessary because:
14 CFR 25.841(a)(2) and (a)(3)

Amendment 25-87 Compliance to be shown with cabin pressure altitude limits for uncontained engine failure Direct compliance would limit maximum aircraft altitude to less than 40,000ft and

would: A) create an economic impact to operators associated with higher fuel

burn B) have an environmental impact due to increased engine emissions associated with higher fuel burn C) reduce competitiveness of the 737-7/- 8/-9 in the aircraft marketplaceRA-13-03728 Enclosure Page 2 of 18

Description of Issue

The 737-7/-8/-9 aircraft is being designed to operate at a maximum cruise altitude of 41,000 ft. Amendment 25-87, Reference (1), established new requirements in § 25.841(a) intended to upgrade the airplane and equipment airwor thiness standards for subsonic tr ansport airplanes operated above 40,000 feet. These were based in part on special cond itions that had been used on type certification of executive business airplanes for many years. Specifically, Amendment 25-87 created three requirements in §§ 25.841(a)(2)(i) , 25.841(a)(2)(ii), and 25.841(a)(3) governing the cockpit/cabin

environment:

§ 25.841(a) subpart; (2) The airplane must be designed so that occupants will not be exposed to a cabin pressure

altitude that exceeds the follo wing after decompression from a ny failure condition not shown to be extremely improbable: (i) Twenty-five thousand (25,000) feet for more than 2 minutes; or (ii) Forty thousand (40,000) feet for any duration.

(3) Fuselage structure, engine and system failure s are to be considered in evaluating the cabin decompression.

The Boeing Company respectfully submits that compliance with §§ 25.841(a)(2), and 25.841(a)(3) as written, with respect only to the considera tion of an uncontained e ngine failure, provides no increase in safety with respect to modern transpor t category jet aircraft when considering the safety record of the fleet over the last 53 years. The fleet has a demonstrated safety record with millions of

hours at altitudes similar to the maximum cruise altitude proposed for the 737-7/-8/-9. Despite the improved descent capability of the 737-7/-8/-9 over previously certificated aircraft of similar category and class, compliance w ith 25.841(a)(2)(i) following an unc ontained engine failure would

limit the 737-7/-8/-9 maximum certificated altitu de. In addition, The Boeing Company assessment of the §25.841(a), Amendment 87, impact on overall fl eet safety raised concerns about several unintended consequences. One such consequence is higher density air tra ffic at altitudes below 40,000 feet as a result of limiting new aircraft w ith wing mounted engines to altitudes below 40,000 feet. This may result in additional cost to mainta in an adequate level of safety for the air traffic
system.

The 737-7/-8/-9 is designed to fly at cruise al titudes that will maximize fuel efficiency. The

reduction in maximum cruise altitude resu lting from compliance with §§25.841(a)(2) and 25.841(a)(3) for uncontained engine failure would signi ficantly impact the marketability of the 737-7/-8/-9. This concern is shared by other ma nufacturers of airplanes with wing-mounted engines seeking new or amended Type certification. No transport category airplane with wing-mounted engines certificated today for operation above 39,000 feet can meet the new cabin altitude limits within the current §§25.841( a)(2) and 25.841(a)(3) without an exemption.

The 737-7/-8/-9 incorporates new technology, lessons learned from previous and current production airplanes, and complies with the latest airworth iness standards (except as noted in 737-7/-8/-9 Certification Basis) throughout to provide a safer, more efficient transpor tation option for operators and occupants. Grant of this pe tition provides the public the benef its of the 737-7/ -8/-9 airplane.RA-13-03728 Enclosure Page 3 of 18

As stated in the Mechanical Systems Harmonization Working Group (MSHWG) report (reference (3)), there is an inherent physiologi cal risk to humans when exposed to high cabin altitudes. In the 737-7/-8/-9 design, The Boeing Company mitigates risk to high cabin altitude exposure by reasonable design requirements, proven design methodologies and operational considerations regardless of the cause of the decompression event. It is intended that the proposed exemption addresses the intended concern for safety w ithout imposing the operational economic penalties driven by §§25.841(a)(2) and 25.841(a)(3) as curren tly written. In the following, The Boeing Company provides:

 a background of the current rule and activities to harmonize it

 a review of the safety history of high altitude commercial flight

 a discussion of hypoxia physiology data upon which rulemaking activities are based

 a discussion of the impact of compliance with uncontained engine rotor burst aspects of the existing rule, as related to economics, envi ronmental, and air traffic considerations.

 proposed risk mitigation

 statements addressing public interest and no adverse impact to safety.

Background on 14 CFR § 25.841( a)(2)(3), Amendment 25-87

Amendment 25-87 to § 25.841(a) was made effective July 5, 1996. The focus of the rule was to codify the special conditions formerly used in th e certification of high alt itude operation, generally applied to general aviation and tr ansport category busine ss jets covering operation up to 51,000 feet. This section was changed without being harmonized with the Joint Aviation Authorities (JAA) or now the European Aviation Safety Agency (EASA). It is noteworthy that the JAA and EASA have not adopted the same regulations as levied in 14 CFR §25.841(a) as promul gated in Amendment 25-87. The JAA INT/POL/25/16, Issue 1, Date: 01.06.03, “Airworthiness Standards for Subsonic Transport Aeroplanes to be operated above an altitude of 41,000 ft,” states, with respect to evaluation of engine rotor burst, “It is JAA opinion that turbine e ngine installations failures should be assessed against the specific requirement of JAR 25.903(d) and should not be part of the present Special Conditions, this is to allow a cons istent approach at the aircraft level...”

The provisions of §§25.841(a)(2) and 25.841(a)(3) of Amendment 25-87 effectively limit new transport category airplanes with wing-mounted engines to operating altitudes well below 40,000 feet. This has major cost impacts since new airp lane models may not be able to compete with existing certificated airplanes or derivative airplanes, which do not have §25.841(a), Amendment 25-87 as part of their certificati on basis. The existing airplanes can cruise at altitudes above 40,000 feet where they are more fuel-efficient.

The Aerospace Industries Association (AIA) and European Association of Aerospace Industries/Association Européenne des Constr ucteurs de Matériels Aeronautique (AECMA) petitioned the Federal Aviation Administra tion to amend 14 CFR 25.841(a), Amendment 25-87, pressurized cabins, and the associated Advisory Ci rcular 25-20. It was sugge sted that the proposed amendment be addressed through the auspices of the Aviation Rulemaking Advisory Committee (ARAC). The petitioners recommended that harmonization with the Joint AirworthinessRA-13-03728 Enclosure Page 4 of 18

Requirements and Transport Canada’s standards be accomplished simultaneously through the ARAC

process.

The petitioners represented the manufacturers of tr ansport category airplane s in the United States and Europe. As such, they have an interest in this rulemaking proposal because new and derivative airplanes designed to meet 14 CFR Part 25 as am ended at Amendment 25-87 will have significantly higher design and operating costs than currently cert ificated airplanes, with no measurable increase in safety. These higher costs impact the ability of manufacturers to devel op new airplanes that can compete with previously approved airplanes. Th e petitioners also iden tified that the economic evaluation conducted by the FAA did not consider the costs associated with applying this new standard to changes to existing type certificates (derivative m odels) when assessing the costs and benefits accruing from the amendment, nor whethe r the new requirement itself could be met by any practical means for any new or derivative airplane.

In July 2001, the FAA assigned the ARAC and the Mechanical Systems Harmonization Working Group (MSHWG) the task of addressing various c oncerns with the regulation, raised by industry, and of reaching a consensus among medical expert s, representatives from the FAA, JAA, Air Transport Association (ATA), Airline Pilots Asso ciation (ALPA), Association of Flight Attendants (AFA) and Aircraft Manufacturers (members with representation in the Aerospace Industries Association (AIA), Aerospace and De fense Industries Association of Europe - Standardization (ASD STAN) [formerly known as the Association of Eu ropean Aircraft and Component Manufacturers (AECMA)] or the General Avia tion Manufacturers Association ( GAMA)). The MSHWG agreed that the existing standard may be conservative relative to engine related failures when considering the associated risks and exposure to safety. The issuance of an FAA Interim Policy, March 2006, Reference (2) is consistent with this position, as is the MSHWG working group report, Reference (3), which identified the existing requirements as being conservative relative to safety. In

consideration of comments received on the draf t Interim Policy and the acceptance of the MSHWG report by Transport Airplane and Engines Is sues Group (TAEIG), the FAA worked with manufacturers to establish appropr iate criteria for 25.841(a) with re spect to an uncontained engine failure. The following proposal is consistent with those criteria a nd similar to exemptions granted for the 787-8, 747-8, 747-8F, A380, A350-900, ERJ 170, and ERJ 190.

Safety History

The original 14 CFR §§25.841(a)(2) and 25.841(a)(3) had the goal of ensuring that no fatalities or permanent physiological harm occurred following a rapid depressurization event. However, the

MSHWG believed that there is an in herent risk to occupant health and safety associated with any rapid depressurization event. Th e MSHWG concluded that all occupants are at some level of risk during a decompression event and the resulting emergency descent, fl ight, and landing. Fatalities may occur during the initial event (i.e., from impact of uncontained engine debris or from being ejected from the airplane). In addition, some cases of permanen t physiological harm could result from hypoxia among those occupants at increased risk due to pre-existing h ealth factors (e.g., age, chronic and acute medical conditions, etc.). Th e following is presented to establish that the demonstrated risk to safety due to rapid depressurizations is non-significant when compared to other risks to safety.RA-13-03728 Enclosure Page 5 of 18

Previously certificated large tran sport aircraft incorporating estab lished design practices have safely operated at altitudes in excess of 40,000 feet for mo re than 30 years, representing many millions of flight hours. Historically, re latively few accidents or incident s have occurred during cruise. According to the statistics, for the period 1959 - 1996, only 6.8 percent of accidents in the worldwide commercial fleet history have o ccurred during cruise; even though th e highest percentage of the flight time (57%) is at cruise (R eference (4)). See Figure 1-1. Mo re recent statis tics, show only 6.0 percent of accidents have occurred during cruise for the period 1994 - 2003, (Reference (5)) and 11 percent of accidents have occurred during cruise for the period 2002 – 2011 (Reference (16)). See Figure 1-2 and 1-3 respectively.

Figure 1-1, Fatalities, Worldwide Commercial Jet Fleet – 1959 - 1996RA-13-03728 Enclosure Page 6 of 18

Figure 1-2, Fatalities, Worldwide Commercial Jet Fleet – 1994 - 2003 

### Accidents and Onboard Fatalities by Phase of Flight

Hull Loss and/or Fatal Accidents - Worldwide Commercial Jet Fleet - 1994 - 2003

Hull loss and/or fatal accidents Onboard fatalities Taxi, load,

parked Takeoff Initial

climb Climb F a t li e s

Cruise Descent Initial approach Final approach Landing 11

3 25 Hull

loss
and/or

fatal

accidents

539

11 17 1,619

788

13 7 14 1,066

13 Initial approach

7%

13%

12% Descent

3%

8%

11% Final approach

6%

16%

3% Percentage of accidents/fatalities

Takeoff

12%

8%

1% Initial

climb

5%

14%

1% Landing

45%

2%

1% Taxi, load, parked

5%

0% Climb (flaps up)

8%

25%

14% Cruise

6%

12%

57% 17% 51%

22% 18% Accidents

Fatalities

Initial approach fix Exposure = percentage of flight time based on flight duration of 1.5 hours

Distribution of accidents and fatalities

0 20 40 60 80 100

0 500 1000 1500 2000

902

541 93

161 Fatalities

865 Final approach fix

16

2003 STATISTICAL SUMMARY, MAY 2004RA-13-03728 Enclosure Page 7 of 18

Figure 1-3, Fatalities, Worldwid e Commercial Jet Fleet – 2002 - 2011

Figure 2 shows fatal accidents by category for the world commercial jet fleet for the period of 1992 to 2001. Note for this period, of the 7,171 fata lities from all causes, none were due to hypoxia resulting from in-flight rapid decompression events at altitudes greater than 25,000 feet. Relative to other causes, decompressions resulting in hypoxic fatali ties are not a significan t accident contributor.RA-13-03728 Enclosure Page 8 of 18

Figure 2: Fatal Accidents by Category

Additionally, an assessment of decompressions since the 2001 completion of the above study through 2011, confirmed there were no additional fatalities due to hypoxia resulting from in-flight rapid decompression. There were 121 additional fata lities related to hypoxia from a single event; the Helios Airways Flight HCY522 accident which was not a decompression ev ent, but a failure of the flight crew to properly confi gure the pressurization system and a subsequent failure to recognize that the aircraft was not pressurized after takeoff, Reference (15). There were no additional deaths or injuries resulting in permanent physiological harm and only two additional incidents were recorded as having resulted in minor barotrauma injuries.

It should also be noted that very few rapid deco mpression events, if any, have exposed aircraft occupants to cabin pressure altit ude profiles that run the risk of permanent harm to occupants. Industry experience shows that very few cases of d ecompressions at high alt itude resulting in death or permanent physiological harm have occurred. The FAA cited 3 cases as examples of uncontained engine failure for consideration. In one case, a DC-10 (cruise flight near Albuquerque, New Mexico) reported several cases of initial decompression sickness apparently with no permanent injuries. However, it was noted th at 24 passengers and crewmembers were brought to the hospital at Kirtland AFB for treatment of symptoms including, barotraumas (ear problems), minor abrasions,

and smoke inhalation. Because there was no know n follow-up on these occupants, there is no way to assess the extent of physiological injuries su stained during this decompression event. The NTSB report, (Reference (6), NTSB repor t NTSB-AAR-75-2) concluded that the rotor burst occurred due to the fact that “The flight crew (was), in eff ect, performing an untested failure analyses on the auto throttle system.” In the second case (Sioux City, Iowa), the aircraft damage was aft of the pressure bulkhead, thus no rapid decompression occurred. The FAA cites this event to estimate the damage if

the debris field had been forward of the pressure bulkhead. In the th ird case (Pensacola, Florida), the airplane was performing a takeoff (not cruise) when the event occu rred and the flight deck crew successfully performed a rejected takeoff. Thus, this case did not encounter a rapid decompression.

It should be noted that the FAA c ited these three cases (Reference (7 )) because they were “data rich” Fatalities by Accident Categories

Fatal Accidents - World Commercial Jet Fleet - 1992 Thr ough 2001

0 500 1,000 1,500 2,000 2,500

Lo

st co

ntro

l CFIT Midair collisio n

In

-flight fir

e Fuel tan

k Landin g Takeo ff confi g

R w y incur s io

n Ice/snow Windshea r Misc . fatalit y

F uel exh au

s t RT O Turbulenc e

Deco m pressio n Unknow nFatalities Total fatalities 2001 fatalities

Sources: Boeing Airplane Safety Engineering (ASE) and Safety Info rmation System (SIS), National Transportation Safety Board (NTS B) D

e c o m

p r e s s i o n

( H

y p o x i a )

> 2 5 K f tRA-13-03728 Enclosure Page 9 of 18

events. In addition to the “data rich” events discussed above, there have been nine other uncontained engine failures at cruise identified to the FAA, Reference (8), however, none of these other events caused a cabin decompression.

The events experienced to date as discussed above were associated with 1 st generation engine technology. Safety enhancement initiatives with re spect to critical rotatin g parts (inspecting for cracks in disks and using continually updated maintenan ce data to refine disk inspection criteria), as well as improvement in engine technology, lessons learned, and 2 nd /3 rd generation engine design practices have resulted in a re duction in uncontained engine failure events. The uncontained engine

failure rates of 2 nd /3 rd generation engines compared to 1 st generation engines has improved by approximately 95% based on historical Bo eing data on uncontained engine failures.

As noted previously regarding the three “dat a rich events” (the Albuquerque, Sioux City, and Pensacola events), only the Al buquerque event resulted in a d ecompression. Furthermore, the Albuquerque event remains an inappr opriate event as a “d ecompression” model, particularly since the NTSB noted that “The flight crew was, in e ffect, performing an untested failure analyses on the autothrottle system” prior to the engine failure , Reference (6), NTSB report NTSB-AAR-75-2.

Figure 3 depicts pressurization ev ents by cause. Note that unc ontained engine failure is an insignificant contributor to th e total number of events.

Figure 3: Pressurization Events by Cause per Flight Hour

In conjunction with the above data, it should be noted that very few decompression events exposed the aircraft occupants to cabin pressure altitude profiles wh ich run the risk of permanent physiological harm. Figure 4 summarizes signif icant transport categor y decompression events 

## Decompression Events by Cause

Pressurization Events per Hour and per Flight, by Cause

0.00E+00 5.00E-07 1.00E-06 1.50E-06 2.00E-06 2.50E-06 3.00E-06 3.50E-06 4.00E-06

U nkn

own

P ress

. Sy

s.

Do or/S

eal

S truc

tura

l Proc ed

ural Eng ine

Sh oo

tdown /B

om

b # Ev/Hr # Ev/Flt

Sources: Boeing Airplane Safety Engineering (ASE) and Safety Information System (SIS), National Transportation Safety Board (NT SB) E

n g i n e

Engine Events Are Rare Contributors To Decompression EventsRA-13-03728 Enclosure Page 10 of 18

resulting in fatalities or incapaci tation. Note that while fataliti es were incurred, none would have been prevented by the intent of § 25.841(a), Amendment 25-87 which was promulgated in large part to prevent death or permanent phys iological harm from hypoxia as a result of a rapid decompression caused by a large hole in the pres sure vessel from an uncontained engine failure. The only fatal

event since this data was taken has been the previously discussed Helios event.

Figure 4: Pressurization Events with Fatality, Incapacitation or Injury

Notes: Total of 2866 pressurization even ts reported 1959-2001. Transport Category Airplanes over 60,000 lbs. Event Altitude and Cabin Altitude were reported for

873 events. Sources: Boeing Airplane Safety Engineering (A SE) and Safety Information System (SIS), National Transportation Safety Board (NTSB)

Of the 18 events that resulted in fa talities, 10 events were at cabin altitude exposures less than those altitudes addressed by § 25.841(a)(2), Amendment 25- 87. In four of the remaining eight events, fatalities were due to injury di rectly attributed to the even t rather than from hypoxia (one catastrophic structure loss, two e ngine failures, and one wheel burst ). The remaining four events were attributed to crew error, un-annunciated loss of pressu rization, and oxygen system failure.

Current generation aircraft, (1980s through 2000s) introduced higher performance permitting higher altitude flight in response to th e need for increased fuel efficien cy and avoidance of increasingly crowded airspace at altitudes below 40,000 feet. The MSHWG report, Reference (3) concluded for the world commercial jet fleet for the period of 1992 to 2001, no hypoxia relate d fatalities were due to in-flight decompression events. This safety reco rd has been maintained even as newer airplanes fly at these higher altitudes more often than older airplanes (see Figur e 5). As stated previously, an assessment of decompressions since the 2001 completion of the above study through 2011

confirmed there were no additional fatalities or permanent physiological harm due to hypoxia All Pressurization Events with associated
Fatality, Incapacitation or Injury

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000

Event AltitudeMaximum Cabin Altitude Fatality/Incapacitation Injury All Pressurization Events with associated
Fatality, Incapacitation or Injury

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000

Event AltitudeMaximum Cabin Altitude Fatality/Incapacitation InjuryRA-13-03728 Enclosure Page 11 of 18

resulting from in-flight rapid decompression, and only two additional incidents resulting in minor barotrauma injuries. As discussed previously, the Helios Airways Flight HCY522 accident was not a decompression event, but a failure of the flight crew to properly configure the pressurization system and a subsequent failure to recognize that the aircraft was not pressurized after takeoff. Based on these facts, the MSHWG report conclusions remain valid. Three separate studies have recently been made to illustrate the extent of ai r traffic operations at high altitude in today’s air traffic system. While today’s numbers are significant, the new genera tion of airplanes similar to the 737-7/-8/-9 are being designed to cr uise at altitudes above 37,000 feet for even longer portions of

their mission.

Figure 5: Frequency of Flights above 37,000 ft. and 40,000 ft. Altitude of New Design Aircraft vs. Older Design Aircraft.

Aerospace Hypoxia Physiology Data

The FAA, and other qualified e xperts agree that the severity of hypoxia exposure to rapid depressurization is determined by th e pressure field and duration of th e event. This is predicated on observations made from flight phys iological and medical experiments. The cabin altitude limits in Amendment 25-87 were developed by the FAA base d in part on recommendations from the FAA’s Civil Aeromedical Institute (CAMI), which we re based on the concept of “Time of Safe Unconsciousness” (TSU) documented by James G. Gaume in his 1970 paper (reference (9)). The study concluded with the statement that, “... a plea must be made for collection of better data.” Gaume’s 1970 paper is only one source in establishing safety basis. It should be understood that the proposed TSU criteria was established as a compen sating consideration to the elimination of the 

### Altitude Reports By Airplane Model

FAA’s Enhanced Traffic Management System (ETMS) Reports for U.S.

0% 5% 10% 15% 20% 25% 30% 35% 40% 45%

70 7 DC - 8 7 2 7

DC

- 9/ 71

7 737 74 7 DC - 1 0 A 3 00 MD-80 767 7 5 7 A310 A320
M D-11 A340 A33 0 777 A31 9 73 7 NGReports Above 40,000 ft

Above 37,000 ft First Flight of Type Prior to 1980 Commercial Aircraft above 28,000 feet

• Data represents reports from one week in Sept. 2000 • Based on position reports every 3 minutes.RA-13-03728 Enclosure Page 12 of 18

passenger oxygen system. Today’s commercial tran sport are required to provide an emergency oxygen system providing additional margin of safety.

The MSHWG agreed additional data based on furthe r study would benefit the establishment of new

standards. In lieu of new data the MSHWG established physiologi cal exposure limits that are conservative with respect to the data available. The MSHWG considered th e available physiological exposure research which included seve ral papers that have been circ ulated in the aerospace medical community, all with the objective of establishing physiological limits to occupants following cabin decompression. It was based on these papers, and c onsideration of the overal l risk to decompression exposure that the MSHWG documented its recomme ndations in the Reference (3) TAEIG accepted report. The following are summaries of the repor ts from recognized Aerospace Medical Doctors addressing physiological information that was considered by the MSHWG:

 James Gaume (Aerospace Medicine) authored a paper substantiating the new rule. According to Gaume, during an emergency descent from 42,000 feet to 5,000 feet for adequate recovery of unconscious passenge rs without any supplemental emergency oxygen to the occupants, with an aircraft emergency descent of 6200 feet per minute and with cabin altitude exceeding 33,000 feet, no more than 1 minute and 42 seconds is considered acceptable. Reference (9): “F actors Influencing the Time of Safe Unconsciousness (TSU) for Commercial Jet Pa ssengers Following Cabin Decompression” by James Gaume, Aerospace Medicine, April 1970.

 Dr. Stanley R. Mohler, a form er director of CAMI (FAA’s Civil Aeromedical Institute), analyzed a number of actual decompression ca ses, including data from studies by Barron, Reference (10), and Gaume. He concluded th at brain damage in the absence of oxygen

starts after about four minutes , and that three minutes above 25,000 feet is a reasonable limit to protect against permanent physiol ogical damage from a cabin decompression occurring at up to 45,000 feet. Reference (11): “Sudden High Altitude Cabin Decompression Immediately Threatens Safety of Aircraft Crew and Passengers” by Dr. Stanley Mohler, Flight Safety Foundati on, Human Factors & Aviation Medicine,

December 1994.

 Dr. Robert Garner, Research Physiologist, Protection and Su rvival Laboratory at CAMI, agrees that limiting cabin altitude exposure to 25,000 feet for up to three minutes and never allowing it to exceed 45,000 feet would prov ide an acceptable le vel of safety. His views on this matter have been communicated to the FAA Transport Standards Staff.

 Draft White paper issued by CAMI - FAA Civil Aerospace Medical Altitude Rule: presented in the MSHWG in July 2002, Referen ce (12), Page 13, states that exposure: if unprotected, passengers to a 41,000 feet alti tude would be approximately equal to exposure at a 40,000 feet altitude.

 “Neurological Study of Simulated Decompressi on in Supersonic Transport Aircraft,” Aerospace Medicine, J.B. Brierley and A. N. Nicholson, August, 1969, Reference (13),

concluded that cabin alt itude exposure above 10,000 feet not more than eight minutes up to peak of 36,000 feet does not cause brain damage.RA-13-03728 Enclosure Page 13 of 18

 “Neurological Sequelae of Prolonged D ecompression,” Aerospace Medicine, A. N. Nicholson and J.R. Ernsting, April 1967, Refere nce (14) concluded th at cabin altitude exposure above 40,000 feet with time exposure of 1 minute and 30 seconds caused brain damage.

In consideration of the above studies, comment s received on the draft Interim Policy, and the acceptance of the MSHWG report by TAEIG, the FAA established appropriate criteria for §25.841(a) with respect to an uncontained engine failu re. These criteria are mo re conservative than those established by MSHWG report. In lieu of any other standard, Boeing will comply with these criteria as presented in the Pr oposed Risk Mitigation discussion pr ovided later in this petition.

Impacts of Compliance with the Uncontai ned Engine Failure Aspect of Rule

The Boeing Company’s 737-7/-8/-9 will fully comply w ith the latest airworthiness standards (except

as noted in the 737-7/-8/-9 Certification Basis) including §§25.841( a)(2) and 25.841(a)(3), Amendment 25-87, except as related to specific structural fa ilure event as defined in 737-7/-8/-9 Certification Basis exception, and as related to an uncontained engine fa ilure event as defined herein.

With respect to uncontained engine failure events, the impact of § 25.841(a), Amendment 25-87 to the aviation industry and the flying public is significant. The “impact” of compliance takes three forms (1) economic which lead to (2) reduced potential for overall safety improvements and (3) environmental.

(1) While it is difficult to place an exact dollar amount on the impact of these new requirements on the 737-7/-8/-9, it is clear that not granting the proposed exemption would have severe impact. This conclusion is based on the reduction in maximum cruise altitude that compliance with §§ 25.841(a)(2) and 25.841(a)(3), Amendment 25-87 as it relates to uncontained engine failure would result in. This reduction in maximum cruise altitude would result in significantly higher operating costs, based on the significant increased fuel burn due to operations at altitudes not optimum for these airplanes. These higher costs will adversely impact the ability of the Boeing 737-7/-8/-9 to compete with previously certificated airplanes which can operate at the more economical cruise altitudes typically in excess of 37,000 feet. In addition, restricting airplane operations to lower altitudes will increase traffic congestion. Three separate studies have shown that the number of operations above 37,000 feet are significant today and the trend is for newer airplanes to cruise at these altitudes for even longer portions of their mission. Limiting operation of new generation airplanes to lower altitudes will result in higher traffic density, which in turn will result in higher cost of safety in order to maintain established air traffic vertical and horizontal separation requirements.

(2) Since the release of Amendment 25-87, a number of amendments to 14 CFR 25 have been released. Each of these amendments has the intent of an increase in aviation safety. The Boeing

737-7/-8/-9 will meet the latest amendments in effe ct at the time of application, except as noted in the 737-7/-8/-9 Certification Basis. The net result is that the 737-7/-8/-9 incorporates the safety

advancements as intended within these late r amendments. Any significant impact to the marketability of the 737-7/-8/-9 will, at a minimu m, result in a reduced number of aircraft withRA-13-03728 Enclosure Page 14 of 18

this higher level of safety as compared with the previous generation of aircraft, or at a maximum, preclude the manufacture of this new model series of aircraft. In either case, Amendment 25-87 results in a reduced potential for overall aviation safety improvements.

(3) As stated in (1) above, the restriction to maximum cruise altitude imposed upon the 737-7/-8/-9 due to compliance with §§ 25.841(a)(2) and 25.841(a)(3), Amendment 25-87 as it relates to uncontained engine failure has a si gnificant adverse impact on 737-7/-8/-9 fuel burn. This additional fuel burn not only increases 737- 7/-8/-9 operating costs, but will also increase engine emissions (e.g. CO 2 ).

Proposed Risk Mitigation

It is The Boeing Company’s assessment that the risk to safety which is attempted to be mitigated by the new rule §§ 25.841(a)(2) and 25.841( a)(3), creates unintended cons equences. The existing fleet has demonstrated safe operations via millions of hours of flight at altitudes similar to those proposed for the 737-7/-8/-9. The risk of rapid depressuri zation following an uncontai ned engine failure is better mitigated by a combination of proven design practices established th rough years of airplane industry experience combined with today’s improved technical capabili ties. It is in tended that the proposed risk mitigation measures augment this exemption request and address the intended concern for safety without the non-commensurate impact s driven by current requirements of §§25.841(a)(2) and 25.841(a)(3).

It must be reiterated that this request for exemption for §§25.841(a)(2) and 25.841(a)(3) is limited to only uncontained engine failures. For rapid depressurization caused by system failures, §§25.841(a)(2) and 25.841(a)(3) will be complied with as amended by Amendment 25-87. For some specific structural failures §§25.841( a)(2) and 25.841(a)(3) at Amen dment 25-87 will be complied with as modified by exception recorded in the 7 37-7/-8/-9 Certification Ba sis. All mechanical and/or functional interfaces that could potenti ally violate the physiological limits imposed by §25.841 (a) are considered. Robust stru ctural and systems design, and th e ability for the airplane to rapidly descend, are key to assuring the safety of ai rplane occupants and are an inherent part of the 737-7/-8/-9 design. The Boeing Co mpany design practices refine the requirements into subrequirements for systems, structures, aerodynamics, and performance in order to assure airplane level compliance.

A key factor in ensuring occupant survivability, after an Uncontained Engine Failure causes a depressurization, is the aircraft de scent performance. The 737-7/-8 /-9 spoiler system is changed to employ greater speedbrake deployment for rapid deco mpression conditions than for normal in-flight operations. Also, the Flight Cont rol Computer (FCC) Level Change mode is changed to be more aggressive controlling th e target speed during emergency descen t. Both changes will improve the 737-7/-8/-9 descent capability compared to the 737-700/800/ 900 airplanes.

The following more specifically addresses The Bo eing Company proposed means of compliance for rapid depressurizations related to uncontained engine failures. Us ing the FAA established criteria (Reference (2)), The Boeing Company proposes to m itigate the risk to occupants from exposure toRA-13-03728 Enclosure Page 15 of 18

high cabin altitudes resulting fr om uncontained engine failure, in part, by implementing the following design requirements on the 737-7/-8/-9 airplane:

 Design Requirement

The airplane must be designed so that occupants will not be exposed to a cabin pressure altitude that exceeds the following after deco mpression from any engine failure condition not shown to be extremely improbable:

(i) Forty-five thousand (45,000) feet for any duration; or (ii) Forty thousand (40,000) feet for one minute; or (iii) Twenty-five thousand (25,000) feet for more than three minutes; or (iv) Ten thousand (10,000) feet for more than six minutes.

In calculating the descent capability of the airplane in or der to meet the cabin altitude requirements, the loss of the failed engine’s contribution as a s ource of power to the systems enabling the descent need be considered. (i.e. If losing power on one e ngine results in loss of a hydraulic system, and that in turn reduces the number of spo ilers that are available, the de scent rate must be based on the capabilities of the degraded system.) System s degradation due to debris damage from an Uncontained Engine Failure need not be considered.

Statement of Public Interest

The Boeing Company Model 737-7/-8/-9 will comply w ith the latest airworthiness standards (except

as noted in 737-7/-8/-9 Cert ification Basis) including §§25.841( a)(2) and 25.841(a)(3), Amendment 25-87, except as related to specific structural failure ev ent as defined in 737- 7/-8/-9 Certification Basis exception, and as related to an uncontained engine failure even t as defined herein. Specific features of the 737-7/-8/-9 design mitigate the sa fety risk to occupants due to a decompression resulting from an uncontained engine failure. Improvements in engine technology, application of lessons learned, and 2 nd /3 rd generation engine desi gn practices have result ed in a reduction in uncontained engine failure events and the risk of a rapid depressurization. As stated above, the Boeing 737-7/-8/-9 will meet all the la test amendments in effect at th e time of appli cation, except as

noted in the 737-7/-8/-9 Certificatio n Basis. The net result is that the 737-7/-8/-9 incorporates the safety advancements as intended within these later amendments.

In addition, the 737-7/-8/-9 will provide im proved operating economics, and environmental improvements. Granting this petition of exemption is in the public interest because it will improve safety relative to previously certificated airplane s, while reducing operationa l costs by reducing the

amount of fuel consumed. The cost of maintaining the level of safe ty within the existing air traffic management system will not be adversely impact ed by continuing to allow operation in the less congested altitudes typically well above 37,000 feet. The reduction in fuel consumed will also result in reduced emissions. These benefits will accrue with no decrease in safety.

Statement of No Adverse Effect on SafetyRA-13-03728 Enclosure Page 16 of 18

The exemption requested will not adversely affect safety. As previously discussed, the 737-7/-8/-9 will comply with §25.841(a) in other asp ects of a rapid depressurization, except as related to specific

structural failure event as define d in 737-7/-8/-9 Certif ication Basis exception, and as related to an uncontained engine failure event as defined herein. In the unlikely event of an uncontained engine failure, the 737-7/-8/-9 desi gn incorporates a high le vel of safety due to it s descent capability and other design features. As conc luded herein, and based on the MS HWG report (reference (3)), and the Interim Policy (referen ce (2)), the world commercial jet fleet has had no hypoxia related fatalities due to in-flight decompression even ts caused by an uncontained engine failure. This safety record has been maintained even as newer airplanes fly at higher altitudes more often than older airplanes. In keeping with time-above-altitude FAA gui dance and the recommendations of the MSHWG report, as adopted by TAIEG, Boeing has incorporated design features that a ppropriately address the risk to safety following an uncontained engine failu re. Therefore, granting of the exemption will not compromise safety to th e airplane occupants.

Summary to be Published in the Federal Register

PETITIONER : Boeing Commercial Airplanes

SECTION OF 14 CFR AFFECTED: 14 CFR 25.841(a)(2)(3)

DESCRIPTION OF RELIEF SOUGHT : To allow relief from the requirements pertaining to cabin decompression following certain extremel y rare uncontained engine failures for the Boeing Model 737-7/-8/-9.

Request to “Waive Pub lication and Comment”

Boeing requests to waive the requirement fo r publication and comments based on similar exemptions granted to the following aircra ft: 787-8, 747-8, 747-8F, A380, A350-900, ERJ 170 and

ERJ 190.

Privileges of the Exemption Ou tside of the United States

Per § 11.81(h), Boeing requests that the privileges of this exemption be extended outside the United States. This extension of privileges is necessa ry for operations based w ithin foreign countries having bilateral agreements with the United States accepting FAA 14 CFR part 25 as their airworthiness standards for transport category airc raft. The 737-7/-8/-9 is intended for the global market place.

ConclusionRA-13-03728 Enclosure Page 17 of 18

The information in this petition for exemption provides evidence that compliance with §§ 25.841(a)(2), and 25.841(a)(3), with resp ect to an uncontained engine fa ilure, provides no increase in safety. The 737-7/-8/-9 provides advancements in technology and safety relative to previously

certified aircraft. Grant of this petition provides the public the bene fits of the 737-7/-8/-9 airplane. Operators will be able to operate the 737-7/-8/-9 wher e it is most efficient and therefore will not face higher operating costs due to increased fuel burn. Fu rthermore, reduced fuel burn will lead to lower engine emissions resulting in positive impact to the environment. By granting this petition for exemption the true benefits of 737-7/-8/-9 will be realized, causing no adve rse effect on safety.

References

1) Amendment 25-87 Final Rule, Docket 26070, Fe deral Register Volume 61, Number 109, June 5, 1996 2) FAA Interim Policy, ANM-03-112-16, Subject: Interim Policy on High Altitude Cabin Decompression (Reference Amendmen t 25-87) Issued March 24, 2006 3) Mechanical Systems Harmonization Work ing Group (MSHWG) Final Report on FAR 25.841(a)(2,3), dated August 2003, submitted to FAA October 21, 2003 4) Statistical Summary of Commercial Jet Ai rplane Accidents, Worldwide Operations, 1959-2002, Published by Boeing Commercial Airplane, May, 2003. 5) Statistical Summary of Commercial Jet Ai rplane Accidents, Worldwide Operations, 1959-2003, Published by Boeing Commercial Airplane, May, 2004. 6) NTSB-AAR-75-2, AIRCRAFT ACCIDENT NATIONAL AIRLINES, INC.,DC-10-10, N60NA NEAR ALBUQUERQUE, NEW MEXICO, November 3,1973 7) Uncontained Engine Failure Fuselage Hole Analysis, Draft Techni cal Note, October 2001 8) Uncontained Engine Damage Database, ACCESS 2000 Database, FAA UED v001, June 10, 2002 9) Factors influencing the time of Safe Unc onsciousness (TSU) for commercial passengers Following Cabin Decompression, Gaume, J ., 1970. Aerospace Medicine, April 1970, pages 382-385 10) Barron, C. and Cook, T., Effects of Variab le Decompressions to 45000 feet, Aerospace Medicine, May 1965, pages 425 - 430 11) Mohler, Dr. Stanley, “Sudden High Altitu de Cabin Decompression Immediately Threatens Safety of Aircraft Crew and Passengers,” Flight Safety Foundation, Human Factors & Aviation Medicine, December 1994 12) Draft White paper issued by CAMI - FAA Civil Aerospace Medical Altitude Rule: presented in the MSHWG in July 2002 13) “Neurological Study of Simulated Decompressi on in Supersonic Transport Aircraft,” Aerospace Medicine, J.B. Brierley and A.N. Nicholson, August, 1969 14) “Neurological Sequelae of Prolonged D ecompression,” Aerospace Medicine, A.N. Nicholson and J.R. Ernsting, April 1967 15) Hellenic Republic Ministry of Transport & Communications, AAIASB Aircraft Accident Report, Helios Airways Flight HCY522, Boeing 737-31S At Grammatiko, Hellas on 14 August 2005, Dated 11/2006 16) Statistical Summary of Commercial Jet Ai rplane Accidents, Worldwide Operations, 1959-2011, published by Boeing Commercial Airplane, July 2012.RA-13-03728 Enclosure Page 18 of 18

17) “Calculation of Flow of Ai r and Diatomic Gases,” Chester W. Smith, Journal of Aeronautical Science, June 1946 18) Advisory Circular 25-20, “Pressurization, Ventilation, and Oxygen Systems Assessment for Subsonic Flight Including High A ltitude Operation”, dated 9/10/96 19) Advisory Circular 20-128A, “Design Consid erations for Minimized Hazards Caused by Uncontained Turbine Engine and Auxiliar y Power Unit Rotor Failure, dated 3/25/1997